The present invention relates to a vehicle fuel tank pressure control apparatus, and particularly to venting apparatus that operates to regulate pressure within a vehicle tank. More particularly, the present invention relates to a tank vent control apparatus that vents fuel vapor from a vehicle fuel tank when fuel is added to the fuel tank and that vents fuel vapor from the vehicle fuel tank under normal running conditions of the vehicle.
During refueling of a vehicle, fuel vapor in the fuel tank is displaced by the incoming fuel and may be discharged from the fuel tank into the atmosphere through the filler neck. To reduce such discharge of fuel vapor, a vapor venting system is often coupled to the fuel tank and configured to permit the fuel vapor in the fuel tank to flow to a vapor-recovery device such as a charcoal canister and to control the timing and flow rate of such fuel vapor from the fuel tank to the vapor-recovery device.
According to the present invention, a fuel vapor vent control apparatus is provided to control venting of fuel vapors from a vehicle fuel tank. The apparatus includes a housing formed to include an inlet, an outlet, and an interior region configured to receive fuel vapor therein through the inlet and discharge fuel vapor therefrom through the outlet. The apparatus further includes a first valve positioned to partition the interior region to form first and second chambers, a first conduit arranged to conduct fuel vapor between the first and second chambers, and a second conduit arranged to conduct fuel vapor between the first and second chambers. The apparatus also includes a second valve positioned to lie in the interior region and arranged to move relative to the first valve to regulate fuel vapor flow through the second conduit.
In preferred embodiments, a primary fuel vapor flow path through the interior region of the housing between the inlet and the outlet is established in the first chamber underneath the first valve to permit fuel vapor to vent through the housing from the fuel tank in communication with the inlet to the vapor-recovery device in communication with the outlet during refueling. The first valve is movable between a closed position blocking the flow of fuel vapor passing through the primary fuel vapor flow path so that it is not discharged through the housing outlet to the vapor-recovery device and an opened position permitting the flow of fuel vapor in the primary fuel vapor flow path to be discharged from the interior region of the housing through the housing outlet to the vapor-recovery device.
The first conduit, second chamber, and second conduit cooperate to establish an auxiliary fuel vapor flow path in the housing to permit fuel vapor to flow between the fuel tank and the vapor-recovery device along a second route whether or not a first route through the primary fuel vapor flow path is opened or closed by the first valve. Fuel vapor flow along the second route through the auxiliary flow path occurs at times when the air pressure in the fuel tank is different than the air pressure in the vapor-recovery device.
The first valve is formed to include the first and second conduits in a preferred embodiment and fuel vapor admitted into the first chamber through the housing inlet can flow through the first conduit and second chamber and past the second valve in the second conduit to reach the housing outlet. The second chamber is located above the first valve.
More and more, states are requiring that vehicle fuel systems be tested periodically to identify systems that do not meet fuel vapor-leakage standards. The tank vent control apparatus with its first and second valves and primary and auxiliary flow paths is adapted to facilitate vehicle fuel system leakage testing.
The second valve is movable relative to the first valve to regulate the flow rate of fuel tank fuel vapor that is discharged from the interior region of the housing through the housing outlet to the vapor-recovery device during, for example, fuel system leakage testing. Specifically, the second valve is positioned to move between a "seated" position engaging a valve seat in the second conduit and on the first valve and permitting a first flow rate of fuel vapor to flow through the auxiliary fuel vapor flow path during normal operation of a vehicle equipped with the tank vent control apparatus and an "unseated" position disengaging the valve seat on the first valve and permitting a second flow rate of fuel vapor to flow through the auxiliary flow path during charging of the fuel system in that vehicle for fuel system leakage testing.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.